Madu Maji sits on a bench at the cattle market in Makurdi, central Nigeria, dragging his bare feet through the dust to stave off boredom.

In the pens, the few cows that remain are little more than skin and bone.

"Our cows can't go grazing in the bush, they are dying now. Herdsmen don't come here anymore," said the elderly Maji, who operates the biggest cattle market in Benue state.

Because of violence in recent months, only about a dozen animals are sold every day, compared to hundreds earlier.

Nomadic cattle herders have all but left Benue state, driven away by fighting over access to resources and a new law banning migratory herding, an age-old practice necessary for the survival of the livestock.

The fertile lands of Benue, veined with a vast network of rivers, attract thousands of herders migrating with their animals in the dry season from desert zones of West Africa.

More are coming as a result of desertification but tension is rising in a country where space is becoming increasingly scarce because of a population explosion.

Nigeria, already home to almost 200 million people, is predicted to become the world's third most populous country by 2050, according to the UN.

The central region has become the scene of almost daily clashes between settled farmers such as the ethnic Christian Tiv and herders, who are mainly Fulani and Muslim.

More than 100 people have been killed since early January, with 100,000 fleeing their homes to safety, according to the local emergency management agency.

After months of inaction, the Nigerian army announced the planned deployment of troops to several states, including Benue, to end the violence.

- Food basket -

Adams Nicholas lost everything when "Fulani killers" armed with assault rifles, pistols and sticks descended on his village of Ancha on the evening of January 4.

"A big number of people came with their cattle and they started to shoot sporadically."

"Two people were killed, our houses were burnt down. They destroyed everything," said the 30-year-old teacher, one of 10,000 displaced people staying at Gbajimba primary school, some 40 kilometres (25 miles) from the state capital.

For miles around, dozens of dusty villages with burnt-out homes have been emptied of their inhabitants. Others live under a night-time curfew.

"We've always been allowing their cows to graze around our farms. But we can't live together anymore. They're animals," Adams said.

In Benue, nicknamed "Food Basket of the Nation", the crisis has morphed into a ethnic and religious crisis, with more and more Tiv openly expressing hatred towards the Fulani, whom they accuse of launching raids from neighbouring states and looting their crops.

"Our people largely depend on farming. We don't have industries here. If you take agriculture away from our people it means you're taking up their lives," Benue's governor Samuel Ortom, an ethnic Tiv behind the controversial ban on open grazing, told AFP.

"We tried every other options, dialogue, meetings, but the killings continued," he added. "This law will provide peace, it is a win-win for both herdsmen and farmers."

- Neglect -

Since its introduction in November last year, the law has led to a standoff between the authorities and the powerful herders unions that still want a nomadic lifestyle and demand its repeal to allow their herds to return to Benue.

In the meantime, the boundary is being enforced.

To see herders and their livestock, you have to go to the neighbouring state of Nasarawa, where livestock markets are teeming with activity.

The herders say armed Christian militias are attacking their cattle, arguing that the law has only emboldened them.

For months, pastors and local politicians have been encouraging farmers to defend themselves in virulent anti-Fulani rants.

"Herdsmen have never been the ones who attacked the villages. They only act in a spirit of revenge," said Muhammed Hussaini, of the Miyetti Allah Cattle Breeders Association, showing gruesome videos of dead cows allegedly killed by farmers.

According to the union leader, the livestock industry has been the poor relation of Nigeria's economy, which has suffered from years of neglect by successive governments.

"Most of the cattle routes are now cultivated by farmers, people even build houses on these routes," he explains.

Yet for many Fulani, leaving Benue isn't a realistic option.

Adamu Mohamed Juda, a 39-year-old "settled" Fulani, has only known Makurdi, where he was born.

"We've been living in peace with Tiv people for decades," said Juda. "We were eating together, we were sleeping together. How did it get to this point?"